[analyzer] Check allocation family more precise.

The statement passed to isTrackedFamily() might be a user defined function calling malloc; in this case we got AF_NONE family for this function.
Now the allocation family is derived from Sym, that holds a family of a real allocator.

This commit is also a movement towards getting rid of tracking memory allocating by unknown means.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178834 91177308-0d34-0410-b5e6-96231b3b80d8